Binder composition for powder coatings

Abstract

The invention relates to a binder composition for powder coatings. The binder composition is substantially based on a mixture of an unsaturated polyester and an oligomer having a plurality of allyl groups and further having at least either ether and ester groups or urethane and optionally ether groups. The oligmer is preferably an allyl ether ester being more preferably the ester of trimethylolpropane diallyl ether or pentaerythritol triallyl ether and a polycarboxylic acid (anhydride).

We claim: 
     
       1. A binder composition for powder coatings consisting essentially of a mixture of an unsaturated polyester, an oligomer having 4-12 allylether groups and further having ester groups, and optionally 0-0.5% by weight relative to said polyester and said oligomer, of a metal-containing catalyst and 0.1-5% by weight relative to said polyester and said oligomer, of an initiator, and wherein the ratio of the unsaturated grous of the polyester to the unsaturated groups of the allyl ether ester is between 50-99 equivalents:1-50 equivalents. 
     
     
       2. A binder composition according to claim 1, wherein said oligomer is an ester of a polycarboxylic acid or anhydride and either trimethylolpropane diallyl ether or pentaerythritol triallyl ether. 
     
     
       3. A binder composition according to claim 1, wherein said oligomer is an ester of a polycarboxylic acid or anhydride and either trimethylolpropane diallyl ether or pentaerythritol triallyl ether. 
     
     
       4. A process for preparing a binder composition according to claim 1 which comprises mixing said polyester and said oligomer in a mixing ratio such that 1-50 equivalents of unsaturation are derived from said oligomer and 50-99 equivalents of unsaturation are derived from said polyester and wherein the total equivalents of unsaturation is 100. 
     
     
       5. A binder composition according to claim 1, wherein said oligomer has a molecular weight less than 1700, and a molecular weight per allyl group of less than 350, and said binder composition has a glass transition temperature of at least 10° C. 
     
     
       6. A binder composition according to claim 1, wherein said oligomer has a molecular weight less than 1700, and a molecular weight per allyl group of less than 350, and said binder composition has a glass transition temperature of at least 10° C. 
     
     
       7. A binder composition according to claim 1 wherein said oligomer has a molecular weight less than 1700, and a molecular weight of less than 350 per allylether group. 
     
     
       8. A binder composition according to claim 1, wherein said oligomer has a molecular weight less than 1700, and a molecular weight of less than 350 per allylether group. 
     
     
       9. A binder composition for powder coatings consisting essentially of a mixture of an unsaturated polyester and an oligomer having allylether groups and further having ester groups, wherein the oligomer having said allylether groups and ester groups has 4-12 allylether groups, said oligomer being obtained by condensing a polycarboxylic acid or anhydride with an allyl ether alcohol. 
     
     
       10. A binder composition according to claim 9 wherein said binder composition consists essentially of said unsaturated polyester;   said oligomer;   0-0.5% by weight, relative to said polyester and said oligomer, of a metal- containing catalyst; and   0.1-5% by weight, relative to said polyester and said oligomer, of an initiator, and wherein the ratio of the unsaturated groups of the polyester to the unsaturated groups of the allyl ether is between 50-99 equivalents:1-50 equivalents.   
     
     
       11. A binder composition according claim 10 wherein said initiator is a photoinitiator. 
     
     
       12. A binder composition according to claim 10, wherein the metal in the metal containing catalyst is at least one selected from the group consisting of cobalt, manganese, lead, copper and vanadium. 
     
     
       13. A binder composition according to claim 10, wherein said initiator is a peroxide. 
     
     
       14. A substrate at least partially coated with a coating, said coating being based on a powder coating composition consisting essentially of a binder composition according to claim 10. 
     
     
       15. A binder composition according to claim 12, wherein said polycarboxylic acid or anhydride are condensed with an allylether alcohol at an allylether alcohol to polycarboxylic acid or anhydride molar ratio of 1:1 to 4:1. 
     
     
       16. A powder coating composition consisting essentially of a binder composition according to claim 1 or 9. 
     
     
       17. A substrate at least partially coated with a coating, said coating being based on a powder coating composition consisting essentially of a binder composition according to claim 1 or 9.